AES E-Library

AES E-Library

Digitally-Controllable Audio Filters and Equalizers

Filters are commonplace elements in audio signal processing. Most well-known filter topologies generate fixed responses with fixed element values, or use variable resistors to alter their responses under user control. This paper explores solutions to varying the response of filters and equalizers using digital-control techniques suitable for computer-controlled systems. High-pass, low-pass, band-pass, band-reject, and parametric topologies are covered using VCAs, resistor ladders, and multiplying DACs as control elements.